docs: def check_conventions_are_cf_16(self, ds):
          '''
          Check the global attribute conventions to contain CF-1.6
  
          CF §2.6.1 the NUG defined global attribute Conventions to the string
          value "CF-1.6"
  
          :param netCDF4.Dataset ds: An open netCDF dataset
          :rtype: compliance_checker.base.Result
          '''
  
          valid = False
          reasoning = []
          if hasattr(ds, 'Conventions'):
              conventions = regex.split(r',|\s+', getattr(ds, 'Conventions', ''))
              for convention in conventions:
                  if convention == 'CF-1.6':
                      valid = True
                      break
              else:
                  reasoning = ['§2.6.1 Conventions global attribute does not contain '
                               '"CF-1.6". The CF Checker only supports CF-1.6 '
                               'at this time.']
          else:
              valid = False
              reasoning = ['§2.6.1 Conventions field is not present']
          return Result(BaseCheck.MEDIUM, valid, self.section_titles['2.6'], msgs=reasoning)